Windows 2000-based clients connect only to the domain controller that was upgraded from Windows NT 4.0 in a mixed-mode domain

After you upgrade the first of multiple Windows NT Server 4.0-based domain controllers to Windows 2000 Server, all of the domain's Windows 2000 Professional-based clients connect to that domain controller for authentication purposes. These clients do not connect to any other domain controller; therefore, the upgraded domain controller may become overloaded. You may also experience loss of fault tolerance capability.

This behavior can occur because Windows 2000 Professional-based clients use only Windows 2000-based domain controllers in a mixed-mode domain.

To resolve this problem, obtain the latest service pack for Windows 2000. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Microsoft has confirmed that this is a problem in Microsoft Windows 2000. This problem was first corrected in Windows 2000 Service Pack 2.

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.
Before you apply the latest service pack to a computer that you want to upgrade from Windows NT Server 4.0 to Windows 2000 Service Pack 1 (SP1), follow these steps on the Windows NT Server 4.0 primary domain controller (PDC):

1. On the computer that is running the Windows NT Server 4.0 PDC, start Registry Editor (Regedt32.exe).
2. Locate and click the following key in the registry:
   HKEY_LOCAL_MACHINE/System/CurrentControlSet/Services/Netlogon/Parameters
3. Click Add Value on the Edit menu, and then add the following registry value:
   Value name: NT4Emulator
   Data type: REG_DWORD
   Radix: Hex
   Value data: 0x1
4. Quit Registry Editor.
5. Apply the latest service pack for Windows NT 4.0.

NOTE: If you run Dcpromo.exe before you add the registry key, all Windows 2000 Professional and member servers must rejoin the domain. You can use the Netdom utility to rejoin member servers.

> You can also use this procedure to upgrade a computer that is running Windows NT 4.0 as a backup domain controller (BDC). If the PDC has already been upgraded and has the NT4Emulator key, you must add the NeutralizeNT4Emulator key to the BDC before you run DCPROMO. This process is described later in this article. You do not need to make any changes to the computers that are running Windows 2000 Professional or to member servers in the domain.

NeutralizeNT4Emulator, as described in the following section.

To perform remote administration on Windows 2000 domain controllers that have the NT4emulator registry value after you install the Windows 2000 Administration Tools package, follow these steps:

1. On the computer that is running Windows 2000 Professional or a member server, start Registry Editor (Regedt32.exe).
2. Locate and click the following key in the registry:
   HKEY_LOCAL_MACHINE/System/CurrentControlSet/Services/Netlogon/Parameters
3. Click Add Value on the Edit menu, and then add the following registry value:
   Value name: NeutralizeNT4Emulator
   Data type: REG_DWORD
   Radix: Hex
   Value data: 0x1
4. Quit Registry Editor.
5. Use Dcpromo.exe to upgrade, and then apply the latest service pack.

For more information about preventing or solving overload problems, click the following article number to view the article in the Microsoft Knowledge Base: